1. Technical Field
The present invention relates to a cutter drive mechanism that transfers power through two gears to move a movable knife in a straight line to a fixed knife to cut media, to a cutter, and to a printer having the cutter.
2. Related Art
JP-A-H10-217182 describes a cutter having a fixed knife, a movable knife, and a cutter drive mechanism that moves the movable knife in a straight cutting direction to and away from the fixed knife. The cutter drive mechanism described in JP-A-H10-217182 also has a motor as the drive source, two cutter drive gears to which drive power is transferred from the motor, and a guide that guides the movable knife.
The two cutter drive gears are disposed in a direction perpendicular to the cutting direction of the movable knife. The two cutter drive gears also mesh together and rotate synchronously. Each cutter drive gear has a drive pin disposed offset from the center of the gear. The movable knife has two slots in which the drive pins of the cutter drive gears are disposed. The long axes of the two slots are perpendicular to each other, and the slots extend in perpendicular directions.
When the two cutter drive gears are driven by the motor, the drive pins move in the cutting direction of the movable knife while moving perpendicularly to each other in the slots. The drive pins therefore meet the end of the slots in the movable knife, and move the movable knife in the retracting direction. During one rotation of the cutter drive gears, the movable knife travels one round trip between the cutting position crossing with the fixed knife, and the standby position where there is a gap between the movable knife and the fixed knife.
If there is a phase difference between the two drive pins due to manufacturing tolerances, for example, in a cutter drive mechanism that uses two cutter drive gears to transfer power to the movable knife, the movable knife may become skewed.
When the movable knife becomes skewed, the behavior (operation) of the movable knife will become unstable if a relatively large amount of play is not provided between the movable knife and the guide. More specifically, when there is little play between the movable knife and the guide, the movable knife becomes skewed, and the movable knife and guide interfere with each other, power is transferred to the movable knife by only one drive pin, and the action of the movable knife becomes unstable. However, providing a large amount of play between the guide and movable knife allows the movable knife to become skewed, the movable knife and the fixed knife do not cross properly, and the quality of cutting the media drops.